Magneto optical current transducer with improved outage performance

Abstract

A MOCT metering system includes a cutoff module that ensures zero output when values from an optical module fall below a threshold value. The cutoff module includes an RMS to DC converter that drives a comparator. The comparator drives a switch that causes the cutoff module to pass through the measured signal unmodified if above a threshold value and to output a zero voltage signal if below a threshold value.

What is claimed is: 
     
       1. A system for sensing current through a conductor and outputting to a meter, the system comprising:
 an optical module including a light source for directing an optical signal in an optical path around the conductor and producing an optical module signal that is a voltage proportional to the current through the conductor; and, 
 a cutout module including a number of circuits configured to receive said optical module signal that is the voltage proportional to the current through the conductor from the optical module and output a cutout module signal to the meter, wherein said cutout module is configured to convert a root mean squared (RMS) value of said optical module signal to a direct current (DC) signal, wherein said cutout module is further configured to output the cutout module signal as the optical module signal unmodified in response to said DC signal of the optical module signal being above a threshold value and said cutout module is further configured to output a zero voltage optical module signal in response to said DC signal being below the threshold value. 
 
     
     
       2. The system of  claim 1  wherein said cutout module includes an RMS to DC converter configured to receive said optical module signal and output said DC signal to a comparator which controls a switch, said switch configured to receive as an input said optical module signal and output said optical module signal through a power amplifier at a switch output in response to said DC signal being above said threshold value. 
     
     
       3. The system of  claim 2  wherein said comparator is configured to cause said switch to pass through said optical module signal through said power amplifier connected to said switch output in response to said DC signal being above said threshold value. 
     
     
       4. The system of  claim 2  wherein said comparator is configured to cause said switch to ground said optical module signal at said power amplifier connected to said switch output in response to said DC signal being below said threshold value. 
     
     
       5. The system of  claim 2  wherein said cutout module further comprises a band pass filter configured to filter said optical module signal before receipt by said RMS to DC converter. 
     
     
       6. The system of  claim 1  wherein said threshold value of the optical module signal is 0.5% of the rated current of the conductor. 
     
     
       7. The system of  claim 1  wherein said threshold value of the optical module signal is 0.25% of the rated current of the conductor. 
     
     
       8. The system of  claim 1  wherein said threshold value of the optical module signal is 1% of the rated current of the conductor. 
     
     
       9. A system for sensing current through a conductor and outputting to a meter, the system comprising:
 an optical module including a light source for directing an optical signal in an optical path around the conductor and producing an optical module signal that is a voltage proportional to the current through the conductor; and, 
 a cutout module including a number of circuits configured to receive said optical module signal that is the voltage proportional to the current through the conductor from the optical module and output a cutout module signal to the meter, the cutout module further being configured to generate a DC signal having a value that is filtered from a root mean squared value of the optical module signal, the cutout module further being configured to output the cutout module signal as the optical module signal unmodified to an amplifier between the cutout module and the meter in response to the DC signal being above a threshold value, and output a zero voltage optical module signal in response to the DC signal being below the threshold value to eliminate erroneous energy registration from the conductor.